Attachment for air cushion confining inflatable trunk structures to air cushion supported vehicles

ABSTRACT

There is disclosed an improved method and mechanism for attachment of flexible/elastic sheet material to &#39;&#39;&#39;&#39;hard structure&#39;&#39;&#39;&#39; portions of surface effect machines or so-called air cushion vehicles or airplanes of the air cushion undercarriage type, so as to provide in such machines inflatable bag or trunk devices or skirts for air sealing purposes. The invention provides for such purposes an improved clamping device for mounting to the vehicle structure the various edge or other portions of an flexible/elastic sheet fabrication without local stress concentrations on the sheet material. Despite subsequent elongation/thinning of the sheet material under operational loadings such as incidental to inflation of the bag or trunk structure material, the clamping device maintains a firm hold on the sheet. The invention features use of a clamp bar about which the sheet fabric is wrapped, and cooperating cradle restraining the sheet to remain in friction-held relation with clamp bar incidental to elongation thereof; thereby avoiding local stress concentrations on the sheet fabric. The clamp bar is mounted so as to be free to swing relative to the cradle whereby high clamping loads are not required, and the clamping efficiency is not critically dependent either upon precompression of the sheet material between the jaws of the clamp device or upon the thickness of the material in either its unloaded or tensioned state.

United States Patent m1 Coles ATTACHMENT FOR AIR CUSHION CONFINING INFLATABLE TRUNK STRUCTURES TO AIR CUSHION SUPPORTED VEHICLES [75] Inventor: Alan V. Coles, Williamsville, NY.

[73] Assignee: Textron, Inc., Providence, R.l.

[22] Filed: Nov. 1, I973 [21] Appl. No.: 411,704

[52] U.S. Cl 244/102 R, 114/67 A, 180/127,

244/100 A [51] Int. Cl. B64c 25/10 [58] Field of Search 244/12 R, 100 A, 100 R,

244/23 R, 101, 102 R, 110 R, 110 11,131, 132,125, 17.17;180/1l6,122, 124,126, 127, 129; 280/150 AB; 114/67 R, 67 A, 123;

Primary ExaminerTrygve M. Blix Assistant Examiner-Barry L. Kelmachter Attorney, Agent, or Firm-Bean & Bean A is 1 Feb. 11, 1975 [57] ABSTRACT There is disclosed an improved method and mechanism for attachment of flexible/elastic sheet material to hard structure portions of surface effect machines or so-called air cushion vehicles or airplanes of the air cushion undercarriage type, so as to provide in such machines inflatable bag or trunk devices or skirts for air sealing purposes. The invention provides for such purposes an improved clamping device for mounting to the vehicle structure the various edge or other portions of an flexible/elastic sheet fabrication without local stress concentrations on the sheet material. Despite subsequent elongation/thinning of the sheet material under operational loadings such as incidental to inflation of the bag or trunk structure mate rial, the clamping device maintains a firm hold on the sheet. The invention features use of a clamp bar about which the sheet fabric is wrapped, and cooperating cradle restraining the sheet to remain in friction-held relation with clamp bar incidental to elongation thereof; thereby avoiding local stress concentrations on the sheet fabric. The clamp bar is mounted so as to be free to swing relative to the cradle whereby high clamping loads are not required, and the clamping efficiency is not critically dependent either upon precompression of the sheet material between the jaws of the clamp device or upon the thickness of the material in either its unloaded or tensioned state.

8 Claims, 8 Drawing Figures PATENTEDFEB] 1 I975 SHEEI 10F 2 FIG. 3

Y PA-TENTED F551 1 I975 SHEET 2 BF. 2

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1 ATTACHMENT FOR AIR CUSHION CONFINING INFLATABLE TRUNK STRUCTURES TO AIR CUSHION SUPPORTED VEHICLES BACKGROUND AND GENERAL DESCRIPTION OF THE INVENTION The invention herein described was made in the course of or under a contract with the Department of the Air Force.

Reference is made for example to prior U.S. Pat. Nos. 26,812 and 3,690,401, which disclose airplane undercarriage systems of the air cushion type employing inflatable bag or trunk type air cushion seals. As shown therein, such trunk constructions typically employ flexible/elastic sheet constructions which are tailored to the geometry of the vehicle fuselage (or hull) from which it is to extend. Many arrangements have been previously devised for attachment of the edges and/or other portions of the skirt or trunk forming sheet fabric to the hard structure of the vehicle so as to provide for example an airtight cell which is inflatable to extend downwardly therefrom, as explained in the aforesaid patents. It is the object of the present invention to provide for use in such cases an improved fabric sheet attachment system; and the accompanying drawing illustrates by way of examples the invention as applied to a specific installation.

THE DRAWING FIG. 1 is a top plan view of an airplane equipped with an air cushion type undercarriage to which the present invention is applied; the cushion air seal trunk component thereof being shown in inflated condition;

FIG. 2 is a side elevational view thereof;

FIG. 3 is an enlarged scale fragmentary sectional view taken as suggested by line 3-3 of FIG. 2; illustrating how a mechanism of the invention may be employed for clamping a central portion of a single sheet of elastic fabric to the hard structure of the airplane so as to provide a dual inflatable-trunk type air cushion sealing arrangement in accordance with the purposes of the present invention;

FIG. 4 is an enlarged scale fragmentary sectional view taken as suggested by the encirclement 4 of FIG.

FIG. 5 is a view taken from one side of FIG. 4;

FIG. 6 is a fragmentary sectional view illustrating an initial stage of the process of connecting (in accordance with the present invention) a peripheral edge portion of the elastic sheet to the outer edge of a panel or door which is adapted to cover the trunk sheet fabric when it is deflated and stowed within the aerodynamic profile of the airplane;

FIG. 7 is a view corresponding to FIG. 6 but showing the final stage of the process of assembly; the trunk sheet fabric being shown in its relaxed condition; and

FIG. 8 corresponds to FIGS. 6 and 7 but shows the sheet fabric under stress such as incidental to inflation of the trunk system for air cushion sealing purposes as shown at FIG. 3.

As shown by way of only one example in the drawing herewith, the invention is applicable to construction of a toroidal shaped air cushion seal of the inflatable trunk type designated 10 which is attached to the bottom structure of an airplane fuselage which is indicated generally at 12. Thus, as explained in the above referred patents, the trunk 10 is adapted to circumscribe the air cushion cavity area beneath the airplane. It is to,be understood however that the present invention is also applicable to any other type or shape of air cushion sealing trunk system, as explained in the aforesaid patents.

The trunk sheet fabric 15 may have been initially fabricated by any preferred method such as shown for example in U.S. Pat. No. 3,690,401; and it is thereby adapted to be attached to the vehicle hard structure along the center line portion of the sheet fabric and around its outer marginal edge portions to the hard structure of the fuselage to provide the desired inflatable trunk system. More specifically, as shown in the drawing herewith, the trunk structure may be constructed from a single continuous sheet of elastic fabric 15', the longitudinal center portion thereof being tucked into a cradle 20 attached to and running along the center of the belly of the fuselage as is illustrated in the accompanying drawing (FIGS. 1, 3, 4, 5). Furthermore, the outer marginal edge portions of the sheet fabric 15 may be attached either to the fuselage per se, or alternatively to the outer edges of door panels 22 which are hinged to the fuselage as indicated at 24. Thus it will be understood that the elastic trunk construction may be thereby mounted on the airplane fuselage so as to be alternately contractible into the aerodynamic'proflle of the airplane and elastically inflated so as to extend therebelow for air cushion confining purposes, as shown in the above referenced patents and in the drawing at FIGS. 1-3 herewith.

However, the present invention is concerned with the means and method of attaching the marginal edge portion (and/or the center-line portion) of the fabric sheet 15 to the hard structure of the machine. As shown at FIGS. 4, 5, the center line support cradle 20 may be provided in the form of an extruded metal rail having by way of only one example mounting flange portions 3030 extending therefrom for engagement by a portion 32 of the hard structure of the machine. The cradle 20 includes downwardly extending ridges or jaws 3434 and a centrally running ridge or jaw 36, thereby defining therebetween a pair of troughs as indicated at 38-38 into which the central portion of the sheet fabric is to be pulled by means of a pair of parallel disposed clamp bars 40-40 which necessarily have a widthwise or transverse dimension less than the distance between facing surfaces of jaws 34 and 36.

As shown at FIGS. 4, 5 these clamp bars may be of tubular form and are pulled inwardly against the sheet fabric so as to force it to fold and move into the troughs 3838 while wrapping around the centrally located jaw 36; this clamping action being performed by means of tie members such as for example bolts 42. When clamping bars 40-40 are positioned by bolts 42 relative to jaws 3434 and 36 in the manner illustrated in FIG. 4, such bars may be considered as being in an operative or clamping position within cradle 20, wherein the bars are disposed diametrically between or intermediate their associated jaws and cooperate therewith to define gates 34'34'. Note that the bolts are headed at the lower ends to engage washers 44, and are threaded at their upper ends into rocker shaped anchors 46. The tubes 40-40 may be apertured as indicated at 48 so as to permit insertion of a socket wrench or the like through the tubes for engaging the bolt heads, for tightening the bolts and drawing the fabric into the cradle.

Thus, it will be appreciated that the central fold portion of the sheet may be drawn up into the cradle by the clamping tubes 40-40 so as to lock its folds into the cradle as illustrated at FIG. 4. Note that the sheet fabric within the cradle is untensioned and of substantially normal thickness condition when wrapped around the central jaw 36. The clamping parts are so dimensioned and relatively arranged that the sheet material may thus be drawn into the cradle when in its untensioned condition without any substantial thinning thereof except at the restricted gates 34-34, where it is pinched or clamped between the facing surfaces of clamping bars 40-40 and jaws 34--34 and 36 at the entrance of the fabric sheet into the troughs of the cradle 20. Then, upon subsequent tensioning of the fabric (incidental to inflation of the trunk structure made therefrom) the depending leg portions 50-50 of the fabric sheet elastically elongate and thin out as illustrated at FIG. 4.

It is a particular feature of the present invention that the tie bolts 42 are free to swing or rock at their upper ends upon the cradle structure; whereby the clamping tubes 40-40 are free to sway or swing laterally as viewed in FIG. 4 in response to variant tensions on the clamping device incidental to inflation of the trunk and operation of the vehicle, without development of local stress concentrations either in the fabric or in the clamp mechanism parts. Note that whereas the fabric sheet is perforated or apertured at intervals to accommodate the tie bolts 42 it is a non-perforated portion of the sheet passing through the gate that is gripped or pinched between the clamp bar and the cradle jaw at the side away from the tensioned (when loaded) side of the fabric. Thus, the operational loading on the fabric is not concentrated in those portions of the sheet which are perforated.

FIGS. 6, 7, 8, illustrate how a marginal edge portion of the sheet fabrication may, in accordance with the invention, be clamped to a hard structural portion of the vehicle, such as for example to the outer edge of a door panel as is shown at 22 (FIGS. 1, 3). These figures also illustrate the sequence of the clamping operation, and thus furnish further explanation of how the fabric sheet may be installed as shown at FIG. 4. FIG. 6 illustrates the first step of the assembly method and depicts a marginal edge portion of the sheet fabric 15 as being placed against the jaws 5252 of a cradle device 54 carried by the door panel 22; the cradle 54 being shaped so as to provide the same trough type configuration as shown at 38 in FIG. 4. In the initial stage the clamp bar 40 is drawn against the fabric sheet so as to pull it into the cradle by means of a plurality of spaced apart tooling bolts 43 until the bar 40 is seated in its operative position as shown at FIG. 7. The tooling bolts 43 may thereupon be replaced by shorter tie bolts as shown at 42 (FIGS. 4, 7, 8).

Note that when the sheet fabric is clamped into the cradle while still in its untensioned condition (FIG. 7) it retains its normal thickness condition except in the regions of the gates 52'52' wherein it is pinched or clamped between the facing surfaces of jaws 52-52 of the cradle and the clamp bar 40. As in the case of FIG. 4, the parts are so dimensioned and arranged that the fabric sheet is thus clamped into the cradle without any substantial thinning thereof, except in the areas of the gates hereinabove referred to. Then upon tensioning of one side portion of the fabric such as incidental to inflation of a bag or trunk made from the fabric, the tensioned side portion of the fabric (as shown at 50, FIG. 8) thins out in accordance with the load thereon. However, as explained in connection with the clamp system illustrated at FIG. 4, the terminal edge portion of the fabric sheet which wraps around the clamp bar 40 and exits at the opposite gate of the mechanism remains of substantially normal untensioned fabric thickness; and the developed clamping action thereon comprises a combination of frictional resistance between the fabric and the bar 40 and the grip imposed upon the fabric between the bar 40 and the terminal gate jaw 52.

Note that in response to the load on the tensioned leg 50 of the fabric the bolts 42 rock upon their anchors 46 relative to the cradle 54 so as to permit the bar 40 to swing laterally within the cradle. This reduces the pinch effect between the cradle jaw and the bar on the fabric at the tensioned leg thereof, and increases the pinch effect on the terminal leg of the fabric; thereby avoiding any undesirable stress concentration on the fabric where it enters the cradle. In consequence the frictional resistance developed between the wrap around portion of the fabric and the clamp bar contributes to the pinch effect exerted on the terminal edge portion of the fabric, and any tendency to concentrate pinch effects on the thinned-out tensioned leg of the fabric may be avoided. The mechanism may be so designed if preferred, so that when the tensioned leg of the fabric sheet is under maximum load and of minimal thickness there will be no pinch effect imposed on that portion of the fabric. Therefore it will be appreciated that the clamping action of the mechanism is vastly improved compared to any system such as wherein the holding effect is concentrated on the tensioned leg of the fabric where it enters the mechanism.

I claim:

1. For use in a surface effect machine, a mechanism for attachment of a flexible/elastic sheet to hard structure of the machine to provide an air cushion type support seal means of the machine, said mechanism comprising in combination:

a cradle member of trough-like form having opposed ridge-like jaw portions, said cradle member being adapted to be attached to the machine and receive a fold of said sheet;

a clamp bar disposed within said fold and dimensioned and disposed to reside in an operative position within said cradle member diametrically between said jaw portions while leaving spacing therebetween and at each side thereof to define a pair of restricted gates through which opposite sides of said sheet pass from within said cradle member, said sheet being pinched between said clamp bar and jaw portions within said gates when said sheet is in an untensioned condition; and a series of tie members connected to and extending from said cradle member into connections with said clamp bar at intervals along its length so as to maintain said clamp bar in said operative position relative to said cradle member, said tie members being swingable relative to said cradle member so as to permit said clamp bar to sway laterally relative to said jaw portions in response to tensioning of one side of said sheet passing through one of said gates so as to reduce the pinch effect between said clamp bar and one of said jaw portions on said one side of said sheet and to increase the pinch effect between said clamp bar and the other of said jaw portions on the other side of said sheet passing through the other of said gates.

2. An attachment mechanism as set forth in claim 1, wherein said tie members are of adjustable length.

3. An attachment mechanism as set forth in claim 1, wherein said tie members are operable to positionally adjust said clamp bar relative to said cradle member.

4. An attachment mechanism as set forth in claim 1, wherein said cradle member includes a pair of parallel arranged trough-like formations at opposite sides of a central ridge-like formation for reception of a pair of folds of said sheet and reception of a pair of parallel disposed clamp bars to retain said folds of said sheet in said cradle member.

5. An attachment mechanism as set forth in claim 1, wherein said tie members extend from said cradle member successively through apertures in said sheet and said clamping bar, and said apertures in said sheet are spaced from portions of said sheet passing through said gates.

6. For use in an airplane of the air cushion undercarriage type, wherein an air cushion confining seal means comprises at least in part an inflatable bag, fabricated from a flexible/elastic sheet, a clamp mechanism for attaching said sheet to the hard structure of said airplane, said clamp mechanism comprising in combination:

a trough-like cradle member fixed to said hard structure and adapted to receive a fold of said sheet therein, said cradle member having a pair of facing jaw portions,

a clamp bar disposed in a sheet clamping position within said cradle member inside said fold of said sheet, said clamping bar being arranged intermediate said jaw portions and cooperating therewith to define gates through which said sheet passes from said cradle member, said sheet being compressed within said gates when said sheet is in an untensioned condition,

and a plurality of spaced apart tie members extending from said cradle member into connections with said clamp bar for maintaining said clamp bar in said clamping position while supporting said clamp bar for free swinging movement laterally within said cradle member relative to said jaw portions to vary the pinch effect on said sheet within said gates.

7. For use in a surface effect machine, a mechanism for attachment of a flexible/elastic sheet to hard structure of the machine to provide an air cushion type support seal means of the machine, said mechanism comprising in combination:

a cradle member adapted to be affixed to said hard structure and having opposed jaw portions defining a trough;

a clamp bar dimensioned to pass between said jaw portions into said trough; and

tie members connecting said clamp bar to said cradle member for moving said clamp bar into said trough between said jaw portions whereby to force said sheet to fold within said trough and wrap around said clamp bar and for maintaining said clamp bar in an operative position intermediate said jaw portions wherein facing surface of said clamp bar and jaw portions cooperate to define a pair of gates arranged adjacent the opposite sides of said clamp bar through which opposite sides of said sheet pass from said trough, said clamp bar being dimensioned relative to said jaw portions to pinch said sheet within said gates while said sheet is in an untensioned condition, said tie members being swingable relative to said cradle member to permit said clamp bar to sway laterally relative to said jaw portions in response to tensioning of one side of said sheet passing through one of said gates so as to reduce the pinch effect between said clamp bar and one of said jaw portions on said one side of said sheet and to increase the pinch effect between said clamp bar and the other of said jaw portions on the other side of said sheet passing through the other of said gates.

8. An attachment mechanism according to claim 7, wherein said tie members extend from said cradle member successively through apertures in said sheet and said clamping bar, and said apertures in said sheet are spaced from portions of said sheet passing through UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,865,352 Dated 975 Inventor(s) Alan V. Coles It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 11, after "Nos.", Re. should be inserted.

Column 6, line 20, "surface" should be surfaces Signed and sealed this 22nd day of April 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks USCOMM-DC 60376-7 69 u.s. aovsnauzm rmu'rmc omcc: 930

FORM PO-OSO (10-69) 

1. For use in a surface effect machine, a mechanism for attachment of a flexible/elastic sheet to hard structure of the machine to provide an air cushion type support seal means of the machine, said mechanism comprising in combination: a cradle member of trough-like form having opposed ridge-like jaw portions, said cradle member being adapted to be attached to the machine and receive a fold of said sheet; a clamp bar disposed within said fold and dimensioned and disposed to reside in an operative position within said cradle member diametrically between said jaw portions while leaving spacing therebetween and at each side thereof to define a pair of restricted gates through which opposite sides of said sheet pass from within said cradle member, said sheet being pinched between said clamp bar and jaw portions within said gates when said sheet is in an untensioned condition; and a series of tie members connected to and extending from said cradle member into connections with said clamp bar at intervals along its length so as to maintain said clamp bar in said operative position relative to said cradle member, said tie members being swingable relative to said cradle member so as to permit said clamp bar to sway laterally relative to said jaw portions in response to tensioning of one side of said sheet passing through one of said gates so as to reduce the pinch effect between said clamp bar and one of said jaw portions on said one side of said sheet and to increase the pinch effect between said clamp bar and the other of said jaw portions on the other side of said sheet passing through the other of said gates.
 2. An attachment mechanism as set forth in claim 1, wherein said tie members are of adjustable lenGth.
 3. An attachment mechanism as set forth in claim 1, wherein said tie members are operable to positionally adjust said clamp bar relative to said cradle member.
 4. An attachment mechanism as set forth in claim 1, wherein said cradle member includes a pair of parallel arranged trough-like formations at opposite sides of a central ridge-like formation for reception of a pair of folds of said sheet and reception of a pair of parallel disposed clamp bars to retain said folds of said sheet in said cradle member.
 5. An attachment mechanism as set forth in claim 1, wherein said tie members extend from said cradle member successively through apertures in said sheet and said clamping bar, and said apertures in said sheet are spaced from portions of said sheet passing through said gates.
 6. For use in an airplane of the air cushion undercarriage type, wherein an air cushion confining seal means comprises at least in part an inflatable bag, fabricated from a flexible/elastic sheet, a clamp mechanism for attaching said sheet to the hard structure of said airplane, said clamp mechanism comprising in combination: a trough-like cradle member fixed to said hard structure and adapted to receive a fold of said sheet therein, said cradle member having a pair of facing jaw portions, a clamp bar disposed in a sheet clamping position within said cradle member inside said fold of said sheet, said clamping bar being arranged intermediate said jaw portions and cooperating therewith to define gates through which said sheet passes from said cradle member, said sheet being compressed within said gates when said sheet is in an untensioned condition, and a plurality of spaced apart tie members extending from said cradle member into connections with said clamp bar for maintaining said clamp bar in said clamping position while supporting said clamp bar for free swinging movement laterally within said cradle member relative to said jaw portions to vary the pinch effect on said sheet within said gates.
 7. For use in a surface effect machine, a mechanism for attachment of a flexible/elastic sheet to hard structure of the machine to provide an air cushion type support seal means of the machine, said mechanism comprising in combination: a cradle member adapted to be affixed to said hard structure and having opposed jaw portions defining a trough; a clamp bar dimensioned to pass between said jaw portions into said trough; and tie members connecting said clamp bar to said cradle member for moving said clamp bar into said trough between said jaw portions whereby to force said sheet to fold within said trough and wrap around said clamp bar and for maintaining said clamp bar in an operative position intermediate said jaw portions wherein facing surface of said clamp bar and jaw portions cooperate to define a pair of gates arranged adjacent the opposite sides of said clamp bar through which opposite sides of said sheet pass from said trough, said clamp bar being dimensioned relative to said jaw portions to pinch said sheet within said gates while said sheet is in an untensioned condition, said tie members being swingable relative to said cradle member to permit said clamp bar to sway laterally relative to said jaw portions in response to tensioning of one side of said sheet passing through one of said gates so as to reduce the pinch effect between said clamp bar and one of said jaw portions on said one side of said sheet and to increase the pinch effect between said clamp bar and the other of said jaw portions on the other side of said sheet passing through the other of said gates.
 8. An attachment mechanism according to claim 7, wherein said tie members extend from said cradle member successively through apertures in said sheet and said clamping bar, and said apertures in said sheet are spaced from portions of said sheet passing through said gates. 